Ultraviolet (UV) rays is one of the primary factors that cause aging and pathological changes to skin. Depending on the wavelength, UV can be classified as UVA, UVB, and UVC. It has been known that over 90% of UV in sunlight is UVA, which has very strong penetration and can penetrate the dermis of skin and cause damage to the skin. Frequent exposure to UVA radiation will cause skin photoaging, reactive oxygen species (ROS) production, DNA damage, collagen wasting, skin flaccidity, etc., and even skin cancer.
Photoaging refers to thickening of skin keratin, desiccation and desquamation of skin, generation of fine lines and dark spots, and skin flaccidity, and the likes due to the acceleration of skin cell aging caused by long term exposure of UV radiation. ROS production will increase oxidation stress in cells, accelerate cell aging and even cause an overactivation of matrix-degrading enzymes, and thus, lead to collagen wasting and skin flaccidity. In addition, UVA may also destroy DNA of cells and cause DNA damage. Accumulation of excessive damaged DNA may not only cause cell aging but also lead to cancerous cells, and thus, results in skin cancer.
Among the skin cancers, melanocytoma is the most lethal. Currently, surgery is the primary method for treating melanocytoma in clinic. For those who are unable to undergo surgery, there is still a need for an effective method for treating or preventing melanocytoma.
In view of the above issues, an effective method for delaying skin cell aging, nursing skin, repairing skin, treating and/or preventing skin cancer is highly desirable in the art. Inventors of the present invention found that Mesembryanthemum crystallinum L. callus extract is effective in reducing the cell damage caused by UV, reducing skin texture and pores, reducing transepidermal water loss, and inducing apoptosis of melanoma cells, and thus, can be used for delaying skin cell aging, nursing skin, repairing skin, treating and/or preventing skin cancer.